TY - JOUR
T1 - Pirouetting pigs
T2 - A large non-primate animal model based on unilateral 6-hydroxydopamine lesioning of the nigrostriatal pathway
AU - Christensen, Anette Bro
AU - Sørensen, Jens Christian Hedemann
AU - Ettrup, Kåre Schmidt
AU - Orlowski, Dariusz
AU - Bjarkam, Carsten Reidies
N1 - Copyright © 2018 Elsevier Inc. All rights reserved.
PY - 2018
Y1 - 2018
N2 - INTRODUCTION: The rotating 6-hydroxydopamine (6-OHDA) rat model has long been important when developing new treatment strategies for Parkinson's disease (PD). Similar non-human primate models have been developed for translational research purposes as large animal models are required by regulatory bodies as an intermediate "phase 0" trial step. However, experimental research in non-human primates encounters several economical and regulatory issues, which may be avoided by the alternative use of pigs as a large animal model for experimental brain research.OBJECTIVE: The primary aim of this study was to examine if unilateral injections of 6-OHDA into the Göttingen minipig nigrostriatal pathway would lead to dopaminergic imbalance and rotational behavior similar to the 6-OHDA unilateral symptomatic model of PD created in other species. The secondary aim was to attempt to verify the rotational behavior as a parkinsonian symptom using subthalamic deep brain stimulation (STN-DBS) to minimize the elicited rotational pattern.MATERIALS AND METHODS: Using an MRI-based stereotactic procedure, ten female Göttingen minipigs were injected unilaterally with 6-OHDA in the nigrostriatal pathway. Postoperatively, an MRI was performed, and the animals were injected with amphetamine and apomorphine and observed for rotational behavior. After a survival period of three months the brains were removed and immunohistochemically stained for tyrosine hydroxylase (TH). One week before sacrifice two animals had DBS electrodes unilaterally implanted in the subthalamic nucleus and various stimulation protocols were conducted during amphetamine challenge.RESULTS: As expected most animals rotated towards the side of the lesion when given amphetamine (3.5-4.0 mg/kg), whereas the predicted opposite response to apomorphine were much harder to reproduce. T1- and T2-weighted postoperative MRI could demonstrate the size and the location of the 6-OHDA injection. Postmortem TH-staining of the final two animals receiving a medial and a lateral injection of 25 μL of 6-OHDA (8 μg/μL, injection rate 5 μL/min) into the diencephalic nigrostriatal pathway showed a prominent unilateral decrease in TH-staining of the substantia nigra pars compacta, the ventral tegmental area and the nigrostriatal pathway on the lesioned side. These two animals displayed spontaneous rotational behavior toward the lesioned side for the first 2-3 days postoperatively, and this behavior could later on be reelicited by amphetamine and attenuated by ipsilateral STN-DBS.CONCLUSION: Female Göttingen minipigs are susceptible to unilateral dopaminergic degeneration when properly injected unilaterally with sufficient amounts of 6-OHDA in the nigrostriatal pathway. The location of the 6-OHDA injections and thus the accuracy of the employed stereotaxy can be verified in vivo using MRI postoperatively. The injected minipigs display unilateral parkinsonism with a well-defined rotational response to amphetamine that may be ameliated by STN-DBS performed on the lesioned side. The response to apomorphine was, however, not consistent, illustrating that further work on this promising non-primate large animal model is needed, before it is fully similar to the established 6-OHDA models in other species.
AB - INTRODUCTION: The rotating 6-hydroxydopamine (6-OHDA) rat model has long been important when developing new treatment strategies for Parkinson's disease (PD). Similar non-human primate models have been developed for translational research purposes as large animal models are required by regulatory bodies as an intermediate "phase 0" trial step. However, experimental research in non-human primates encounters several economical and regulatory issues, which may be avoided by the alternative use of pigs as a large animal model for experimental brain research.OBJECTIVE: The primary aim of this study was to examine if unilateral injections of 6-OHDA into the Göttingen minipig nigrostriatal pathway would lead to dopaminergic imbalance and rotational behavior similar to the 6-OHDA unilateral symptomatic model of PD created in other species. The secondary aim was to attempt to verify the rotational behavior as a parkinsonian symptom using subthalamic deep brain stimulation (STN-DBS) to minimize the elicited rotational pattern.MATERIALS AND METHODS: Using an MRI-based stereotactic procedure, ten female Göttingen minipigs were injected unilaterally with 6-OHDA in the nigrostriatal pathway. Postoperatively, an MRI was performed, and the animals were injected with amphetamine and apomorphine and observed for rotational behavior. After a survival period of three months the brains were removed and immunohistochemically stained for tyrosine hydroxylase (TH). One week before sacrifice two animals had DBS electrodes unilaterally implanted in the subthalamic nucleus and various stimulation protocols were conducted during amphetamine challenge.RESULTS: As expected most animals rotated towards the side of the lesion when given amphetamine (3.5-4.0 mg/kg), whereas the predicted opposite response to apomorphine were much harder to reproduce. T1- and T2-weighted postoperative MRI could demonstrate the size and the location of the 6-OHDA injection. Postmortem TH-staining of the final two animals receiving a medial and a lateral injection of 25 μL of 6-OHDA (8 μg/μL, injection rate 5 μL/min) into the diencephalic nigrostriatal pathway showed a prominent unilateral decrease in TH-staining of the substantia nigra pars compacta, the ventral tegmental area and the nigrostriatal pathway on the lesioned side. These two animals displayed spontaneous rotational behavior toward the lesioned side for the first 2-3 days postoperatively, and this behavior could later on be reelicited by amphetamine and attenuated by ipsilateral STN-DBS.CONCLUSION: Female Göttingen minipigs are susceptible to unilateral dopaminergic degeneration when properly injected unilaterally with sufficient amounts of 6-OHDA in the nigrostriatal pathway. The location of the 6-OHDA injections and thus the accuracy of the employed stereotaxy can be verified in vivo using MRI postoperatively. The injected minipigs display unilateral parkinsonism with a well-defined rotational response to amphetamine that may be ameliated by STN-DBS performed on the lesioned side. The response to apomorphine was, however, not consistent, illustrating that further work on this promising non-primate large animal model is needed, before it is fully similar to the established 6-OHDA models in other species.
KW - 6-hydroxydopamine
KW - Amphetamine
KW - Apomorphine
KW - Dopamine
KW - Göttingen minipig
KW - Parkinson's disease
UR - http://www.scopus.com/inward/record.url?scp=85042876153&partnerID=8YFLogxK
U2 - 10.1016/j.brainresbull.2018.02.010
DO - 10.1016/j.brainresbull.2018.02.010
M3 - Journal article
C2 - 29462643
SN - 0361-9230
VL - 139
SP - 167
EP - 173
JO - Brain Research Bulletin
JF - Brain Research Bulletin
ER -